两个定积分呢问题?
来源:学生学帮网 编辑:学帮网 时间:2024/06/25 21:33:56
两个定积分呢问题?
(1)
∫(0->2π) (cosθ)^2 dθ
=(1/2)∫(0->2π) [1+cos(2θ)] dθ
=(1/2)[θ+sin(2θ)/ 2](0->2π)
=π
(2)
(1/4)∫(0->3) r^2 dr^2
=(1/8)[r^4](0->3)
= 81/8
第二个是对的
两个定积分呢问题?
(1)
∫(0->2π) (cosθ)^2 dθ
=(1/2)∫(0->2π) [1+cos(2θ)] dθ
=(1/2)[θ+sin(2θ)/ 2](0->2π)
=π
(2)
(1/4)∫(0->3) r^2 dr^2
=(1/8)[r^4](0->3)
= 81/8
第二个是对的